The energy stores of electric vehicles are usually charged at a charging column, which is connected to a public power supply system. For this purpose, use is generally made of charging systems, which are designed exclusively for a low-voltage connection, that is to say below 1500 V and, for example, for a 400 V three-phase system.
However, charging a plurality of vehicles in what are known as car charging parks requires higher powers, with the result that it is necessary to resort to the medium-voltage grid. The grid transformers required for this purpose, however, have disadvantages in terms of size and cost and are also linked to the grid frequency, as a result of which high losses occur.
The prior art has therefore disclosed charging systems that manage without a grid transformer. These charging systems are equipped with a series connection of power semiconductors for that purpose. However, such an interconnection arrangement of power semiconductors requires a very high degree of complexity with regard to balancing, since otherwise there is a high risk of uneven distribution of the voltage to the individual semiconductors and therefore a high risk of breakdowns of the individual semiconductors.